The invention relates to a method and apparatus for photometry from plural points of an automatic exposure camera, and more particularly, to a novel method of photometry in which spotwise photometric means of the storage type is provided in an automatic exposure camera and is used to effect photometry from plural points and the values obtained are averaged, and a photometric apparatus used to carry out the method. When power is provided to the photometry circuit, photometry is successively conducted with each new value replacing the previously generated value, so long as the photometry circuit receives operating power.
As is well recognized, a photometric technique in conventional automatic exposure cameras may be categorized into an average photometry and a spotwise photometry type. The average photometry may be subdivided into one in which an average over the full image field is taken and another in which the emphasis is placed on a central region. A tolerable result is obtained for ordinary objects being photographed by this average photometry method, which is more easy to use than the spotwise photometry method and hence is generally employed in almost all cameras of general use.
The spotwise photometry method is effective when the exposure value is to be controlled in accordance with a bright or dark portion, or a highlight and a shadow, of an object being photographed in which the ratio of brightness between these portions is high. However, its operation is troublesome and is highly susceptible to the production of a picture having an improper exposure. In the past, some cameras have been offered on the market in which the photometry is directed to only a central region of the image field. However, the composition is difficult to define, and there is no automatic exposure camera currently which adopts such photometry.
From the foregoing, it can be concluded that the average photometry method is superior to the spotwise photometry method when taking pictures of ordinary objects. However, practical objects being photographed are not limited to those having a low brightness ratio, but there are a number of objects exhibiting a high brightness ratio such as those in rear light, those on a stage, and those framed by a window through which the exterior sight is composed. In particular, the chance of taking pictures of objects exhibiting a high brightness ratio increases with an increasing level of skill of a photographer. When a picture is taken of an object being photographed which exhibits a high brightness ratio by utilizing an automatic exposure camera which adopts the average photometry method, the exposure is controlled in accordance with the averaged brightness of the object, preventing the intended composition of a photographer from being fully achieved as might be achieved by controlling the exposure in accordance with the highlight or shadow.
In the prior art practice, when taking a picture of an object of a special kind such as described immediately above, a so-called spot exposure meter having a very small photometric angle is used to effect photometry from plural points on the object being photographed. An exposure factor such as exposure period is determined on the basis of information relating to the brightness of the object thus obtained, and the photographic intention where a proper exposure should be given and what degree of brightness the shadow should exhibit, and the camera is manually operated to take a picture. Where an object being photographed is accessible as when taking a picture in a studio, an exposure meter of the type which receives incident light is used to effect photometry of desired plural points on the object in order to determine an exposure factor or factors before the camera is manually operated to take a picture. However, the use of an exposure meter which is separate from the camera to effect spotwise photometry to determine exposure factors requires a troublesome procedure and hence a complex calculation, and is also time consuming.